This invention generally relates to digital computers for use in data processing systems and more specifically to the establishment of initial operating conditions in such digital computers.
A conventional data processing system includes a digital computer for processing data in response to a sequence of instructions in a program, a random access memory which stores the data and instructions, and peripherals which transfer information to and from the digital computer, the random access memory or other peripherals. In addition, the digital computer conventionally includes an operator's console. The console typically contains switches for loading address and data signals into the digital computer and also for controlling data and address transfers between the console and the digital computer. It also contains lights for displaying the contents of various locations and other information concerning the status of the digital computer.
When it is desired initially to energize a conventional data processing system, there are generally no instructions in the random access memory to guide the digital computer. Similarly, the contents of the memory essentially are erased if it does not retain information when the power supply is turned off. In either case, a system operator uses the console switches to manually load a "bootstrap" program into the memory. The bootstrap program usually contains a few instructions which can then be processed by the digital computer to bring in other instructions or data in a second program. The second program might comprise a "bootstrap loader" which contains instructions for reading information from a particular peripheral, such as a keyboard or tape reader. When the random access memory contains this information, the digital computer can thereafter coact with the peripheral to transfer other programs into the memory through that peripheral.
The operator also uses the switches and lights for diagnosing computer operations. Certain control switches enable the operator to examine and alter data in identified locations. Other switches enable the operator to analyze the execution of a computer program on a step-by-step basis.
Although consoles generally are found on all digital computers, they do introduce several drawbacks for the data processing system user. For example, an operator must be physically present at the digital computer site to initialize the digital computer or to perform diagnostic operations through the console. If a power failure or other operating problem occurs, only the operator can initialize or correct the problem. Again, the operator generally must be physically present at the digital computer site.
Moreover, the console panel includes a large number of switches and lights as console elements. These elements increase the manufacturing expense of the digital computer because the panel must be manufactured to support these elements and because these elements must be properly wired into the digital computer circuits. As the costs of the electronic circuits in a digital computer continue to decrease with the introduction of large scale and grand large scale integration manufacturing techniques, the console manufacturing expense can constitute a significant portion of the total cost of the digital computer.
Therefore, it is an object of this invention to provide a digital computer in which computer initialization and diagnostics are simplified.
Another object of this invention is to provide a digital computer in which initialization and diagnostic operations can be performed from a location which is remote with respect to the digital computer.
Still another object of this invention is to eliminate the need for complex switching and lighting arrangements used in conventional digital computer consoles.